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Ancient shark had colossal bite
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Ancient shark had colossal biteBy Jennifer Carpenter Science reporter, BBC News
A new study of the extinct creature's skull shows it had an almighty bite, making the prehistoric fish one of the most fearsome predators of all time. All the more remarkable, scientists say, because the crushing force came from jaws made of cartilage, not bone. The researchers report their skull work in the Journal of Zoology. The Carcharodon megalodon super-shark swam in the oceans more than a million-and-a-half years ago. It grew up to 16m (52ft) in length and weighed in at 100 tonnes - 30 times heavier than the largest great white - and must have been one of the most formidable carnivores to have existed. "Pound for pound, your common house cat can bite down harder, " explained Dr Stephen Wroe of the University of New South Wales, Australia. "But the sheer size of the animal means that in absolute terms, it tops the scales."
The approach is a common one in advanced design and manufacturing, and allows engineers to test the performance of load-bearing materials, such as the metal in the body and wings of an aeroplane. CT (X-ray) scans were taken of megalodon remains to construct a high-resolution digital model. A model of a modern 2.4m-long male great white shark ( Carcharodon carcharias ) was developed for comparison. The model of Megalodon's muscles was based on those of the great white, and the simulations were then loaded with forces to see how the two skulls, jaws, teeth and muscles would have coped with the mechanical stresses and strains experienced during feeding. MEGALODON COMPARED WITH THE GREAT WHITE SHARKBy looking at the distribution of stress and strain on the sharks' jaws, researchers found that the largest great whites have a bite force of up to 1.8 tonnes, three times the biting force of an African lion and 20 times harder than a human bites. Megalodon, though, is more impressive. It is estimated to bite down with a force of between 10.8 to 18.2 tonnes. The team said biting with such force was quite a feat given that the jaws of these ancient creatures were made of flexible cartilage. In contrast to most other fish, sharks' skeletons are made up entirely of cartilage. Scientists think that cartilage, being a much lighter material than bone, is one adaptation that allows sharks to swim without the aid of a swim bladder.
The scientists' study shows that the cartilaginous jaw is almost as strong as a bony jaw of the same size - losing only a few percent - in measures of bite force. What is more, the elasticity of the cartilage jaw increases the gape of the sharks to devastating ends. "The shark's upper jaws can be dislocated: the whole upper and lower jaw pull out and forward as the shark twists and shakes its head from side to side to bite a chunk out of its prey," explains Dr Wroe. These sharks feed on very large prey: the great white shark eats sea lions and the megalodon is thought to have eaten whales. "These sharks ambush their prey and immobilise them with a bite, then wait for them to die," Dr Wroe told BBC News. "They are actually delicate feeders and take care not to damage their teeth by biting down too hard on the large bones of their prey." To keep their teeth sharp, sharks have a battery of them that is continually replaced. It is the combination of their size, their razor-sharp teeth and the element of surprise that makes these sharks such deadly predators. Human brains pay a price for being bigMetabolic changes responsible for the evolution of our unique cognitive abilities indicate that the brain may have been pushed to the limit of its capabilities. Research published today in BioMed Central's open access journal Genome Biology adds weight to the theory that schizophrenia is a costly by-product of human brain evolution. Philipp Khaitovich, from the Max-Planck-Institute for Evolutionary Anthropology and the Shanghai branch of the Chinese Academy of Sciences, led a collaboration of researchers from Cambridge, Leipzig and Shanghai who investigated brains from healthy and schizophrenic humans and compared them with chimpanzee and rhesus macaque brains. The researchers looked for differences in gene expression and metabolite concentrations and, as Khaitovich explains, "identified molecular mechanisms involved in the evolution of human cognitive abilities by combining biological data from two research directions: evolutionary and medical". The idea that certain neurological diseases are by-products of increases in metabolic capacity and brain size that occurred during human evolution has been suggested before, but in this new work the authors used new technical approaches to really put the theory to the test. They identified the molecular changes that took place over the course of human evolution and considered those molecular changes observed in schizophrenia, a psychiatric disorder believed to affect cognitive functions such as the capacities for language and complex social relationships. They found that expression levels of many genes and metabolites that are altered in schizophrenia, especially those related to energy metabolism, also changed rapidly during evolution. According to Khaitovich, "Our new research suggests that schizophrenia is a by-product of the increased metabolic demands brought about during human brain evolution". The authors conclude that this work paves the way for a much more detailed investigation. "Our brains are unique among all species in their enormous metabolic demand. If we can explain how our brains sustain such a tremendous metabolic flow, we will have a much better chance to understand how the brain works and why it sometimes breaks", said Khaitovich.
* 12:05 04 August 2008 * NewScientist.com news service
Even Jules Verne did not foresee this one. Deep down at the very bottom of the Atlantic Ocean, geochemist Andrea Koschinsky has found something truly extraordinary: "It's water," she says, "but not as we know it." At over 3 kilometres beneath the surface, sitting atop what could be a huge bubble of magma, it's the hottest water ever found on Earth. The fluid is in a "supercritical" state that has never before been seen in nature. The fluid spews out of two black smokers called Two Boats and Sisters Peak. Koschinsky, from Jacobs University in Bremen, Germany, says it is somewhere between a gas and a liquid. She thinks it could offer a first glimpse at how essential minerals and nutrients like gold, copper and iron are leached out of the entrails of the Earth and released into the oceans.
In 2005, a team of scientists including Koschinsky visited 5° south, as part as a six-year project to investigate the southern end of the mid-Atlantic Ridge. There, they discovered a new set of vents, which they revisited in 2006 and 2007, lowering a thermometer into them each time. Computer models suggest that the fluid that comes out of these black smokers initially seeps down into surrounding cracks in the seabed, gradually getting deeper and hotter as it approached the Earth's magma. Eventually, at 407 °C and 300 bars of pressure, the water becomes supercritical. Because supercritical water is far less dense than liquid water, it shoots up to the seabed like a bubble and it is spat out into the ocean through vents. A black smoker (Image: NOAA) Powering lifeFrom their first visit in 2005, the team found temperatures in the vents were at least 407 °C, and even reached 464 °C for periods of 20 seconds. Supercritical water leaches metals and other elements out of rock far more efficiently than liquid water or vapour. Gold, copper, iron, manganese, sulphur and many more are brought out of the Earth's guts when the water is ejected from the black smokers. Some, such as sulphur, provide energy to the locally adapted organisms, which have no light to power a food chain. Manganese is similarly used as an energy source by microbes higher up in the water column. Iron is essential for the growth of all phytoplankton. Koschinsky estimates up to half the manganese and one tenth of the iron found in the oceans could come from vents. But because supercritical fluids have never been observed in nature, little is really known about how this happens. Melting equipment"We stand to greatly improve our models of fluid circulation and heat and mass transfer," says Margaret Tivey, a geochemist at the Woods Hole Oceanographic Institute (WHOI) in Massachusetts. Because of the extreme conditions, computer models are the only way of understanding the processes that drag elements out of the seafloor at hot vents. "It's not yet possible to drill into active vents," explains Koschinsky. "Temperatures are so high, much of drilling equipment would melt and joins would not work anymore." The data from the new vents will be invaluable in testing the models. "The findings are significant," says Dan Fornari, also of WHOI. "The high temperature of the venting is especially interesting as this [mid-ocean ridge] does not spread very rapidly." The Pacific spreads faster than the Atlantic, bringing magma closer to the seabed. For this reason, geochemists expected to find supercritical seawater there too. "So one can presume that this portion of the south mid-Atlantic ridge is in a very magmatic phase and has been for a few years," adds Fornari. 'Dry as a biscuit'In the Pacific, vents tend to cool after a year or so, but it is likely that the Two Boats and Sisters Peak have been active since an earthquake shook the region in 2002. "The magma body underneath is probably enormous," says Koschinsky. Her colleague Colin Devey of the University of Kiel in Germany is not so sure. "The explanation could be that there's lot of magma, but after a few more years of high temperatures, it's going to get to the point where it will be embarrassing how much magma there needs to be to maintain them for that long." He thinks the long-standing temperatures could indicate something more fundamental. The fact that vents cool much more quickly in the Pacific could indicate the crust there is much more water-logged than it is in the Atlantic, where it could be "dry as a biscuit". "If that turns out to be the case then we will have taken down some very, very holy grails," says Devey. Journal reference: Geology (DOI: 10.1130/G24726A.1)
* 14:02 04 August 2008 * NewScientist.com news service
Government efforts to gird for the next influenza pandemic – bird flu or otherwise – ought to take notice and stock up on antibiotics, says John Brundage, a medical microbiologist at the Armed Forces Health Surveillance Center in Silver Spring, Maryland. Brundage's team culled first-hand accounts, medical records and infection patterns from 1918 and 1919. Although a nasty strain of flu virus swept around the world, bacterial pneumonia that came on the heels of mostly mild cases of flu killed the majority of the 20 to 100 million victims of the so-called Spanish flu, they conclude.
"We agree completely that bacterial pneumonia played a major role in the mortality of the 1918 pandemic," says Anthony Fauci, director of National Institute for Allergy and Infectious Disease in Bethesda, Maryland, and author of another journal article out next month that comes to a similar conclusion. Double whammy That pneumonia causes most deaths in an influenza outbreak is well known. Late 19th century physicians recognised pneumonia as the cause of death of most flu victims. While doctors limited fatalities in other 20th-century outbreaks with antibiotics such as penicillin, which was discovered in 1928, but did not see use in patients until 1942. This is not to say that flu viruses do nothing, says Jonathan McCullers, an expert on influenza-bacteria co-infections at St Jude Children's Research Hospital in Memphis, Tennessee. McCullers' research suggests that influenza kills cells in the respiratory tract, providing food and a home for invading bacteria. On top of this, an overstressed immune system makes it easier for the bacteria to get a foothold. However, the sheer carnage of 1918 caused many microbiologists to reconsider the role of bacteria, and some pointed their fingers firmly at the virus.
When US government scientists resurrected the 1918 strain in 2005, the virus demolished cells grown in a Petri dish and felled mice by the dozen. "The 1918 pandemic is considered to be – and clearly is – something unique, and it's widely understood to be the most lethal natural event that has occurred in recent human history," Brundage says. But to reassess this conclusion, he and co-author Dennis Shanks, of the Australian Army Malaria Institute in Enoggera, Queensland, scoured literature and medical records from 1918 and 1919. The more they investigated, the more bacteria emerged as the true killers, an idea now supported by most influenza experts. For instance, had a super virus been responsible for most deaths, one might expect people to die fairly rapidly, or at least for most cases to follow a similar progression. However, Shanks and Brundage found that few people died within three days of showing symptoms, while most people lasted more than a week, some survived two – all hallmarks of pneumonia. Local bugs Military health records for barracks and battleships also painted a different picture. New recruits – men unlikely to have been exposed to resident bacteria – died in droves, while soldiers whose immune systems were accustomed to the local bugs survived. And most compelling, Brundage says, medical experts of the day identified pneumonia as the cause of most deaths. "The bottom line is we think the influenza virus itself was necessary – but not sufficient – to cause most of the deaths," he says. As the world's health experts prepare for the next influenza pandemic, many have looked to 1918 as a guide, planning for a deadly super-virus. The H5N1 bird flu strains jetting around the world seem to kill humans without the aid of bacteria, but those viruses aren't fully adapted to humans, McCullers says. If H5N1 does adapt to humans, bacteria may play a larger role in deaths, he adds. "Everyone is focused exclusively on the virus, and that's probably not the best idea," he says. Antibiotics and vaccines against bacterial pneumonia could limit deaths in the next pandemic. And while an effective influenza vaccine should nip an outbreak in the bud, such a vaccine could take months to prepare and distribute. "The idea of stockpiling [bacterial] vaccines and antibiotics is under serious consideration," says Fauci, who is on a US government taskforce to prepare for the next flu pandemic. At a recent summit on pandemic influenza, McCullers said health authorities were increasingly interested in the role bacteria might play, but there had been little action taken. "There's no preparation yet. They are just starting to get to the recognition stage," he says. "There's this collective amnesia about 1918." Journal reference: Emerging Infectious Disease (DOI: 10.3201/eid1408.071313)
* 22:00 04 August 2008 * NewScientist.com news service
Could injections of vitamin C help treat cancer? That's the suggestion from a new study in mice – and trials are already under way to test similar injections in people. But some cancer specialists are sceptical, and fear that desperate patients will be prompted to start taking large doses of the vitamin. That may be dangerous, because antioxidants such as vitamin C could undermine the effectiveness of standard cancer drugs and radiation therapy. Excitement over the idea of treating cancer with vitamin C grew in the 1970s after the Nobel prize-winning chemist Linus Pauling suggested that it helped terminally ill patients survive for longer. However, in 1985, two placebo-controlled trials found no effect of taking vitamin C pills. In the current study, researchers led by Mark Levine of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland, gave vitamin C to mice intravenously. Oxidation boost The researchers injected immune-deficient mice with cells from three aggressive human cancers – ovarian and pancreatic tumours, plus a form of brain cancer called glioblastoma – and found that vitamin C injections slowed tumour growth by up to 53%. By injecting into the bloodstream, Levine explains, it is possible to get much larger amounts of the vitamin to a tumour than is possible with oral supplements. While vitamin C is usually an antioxidant, under these circumstances it causes the formation of hydrogen peroxide, a powerful oxidising agent that kills cancer cells. Levine suggests that intravenous vitamin C could be a useful addition to conventional cancer therapy. His team has also found that women in a preliminary clinical trial are getting similar doses of vitamin C to those seen in the experimental mice. "It's pharmacologically achievable," Levine says. That trial, led by Jeanne Drisko of the University of Kansas in Kansas City, aims to recruit 50 women to test the safety of giving intravenous vitamin C, plus other antioxidants given orally, on top of existing therapies for ovarian, cervical or uterine cancer. Although there is little evidence that it works in humans, Drisko's clinic also offers intravenous vitamin C to paying patients. Self-medication risks Meanwhile, the Cancer Treatment Centers of America (CTCA) in Zion, Illinois, is testing the safety of intravenous vitamin C in late-stage cancer patients for whom there is no other treatment option. So far, 10 out of a planned 18 patients have been enrolled into the trial. Definitive answers on the effectiveness of intravenous vitamin C will only come from subsequent larger trials. But given recent experiences with a drug called DCA, which some patients began taking without medical supervision after reading about promising results on cancer cells, there are concerns that patients may take matters into their own hands by injecting themselves with vitamin C or taking large doses of vitamin C pills. Many cancer patients take antioxidant vitamins, often without telling their doctors. While Drisko and other backers of complementary approaches suggest that antioxidants can aid therapy and reduce side-effects, conventional chemotherapy and radiotherapy are thought to work in part by generating free radicals which kill cancer cells. Because antioxidant vitamins can mop up these radicals, they may interfere with cancer therapy, other researchers warn. "You want to make sure you're not taking supplemental vitamins," says David Agus, an oncologist at the Cedars-Sinai Medical Center in Los Angeles.
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Liquids boil and evaporate as temperature and pressure rise. But push both factors beyond a critical point and something odd happens: the gas and liquid phase merge into one supercritical fluid. For water, this fluid is denser than vapour, but lighter than liquid water.
Medical and scientific experts now agree that bacteria, not influenza viruses, were the greatest cause of death during the 1918 flu pandemic.